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Testing tonearm bearings

Grbluen

Grbluen

Super Member
Happy Easter everyone!

I'm looking for some help with testing the bearings in my tonearms. I have a relatively new Jelco TK-850M. I think the specs are 30mg in both directions. I have floated the arm, and I'm getting significantly less in both directions. I know lower is better. Does anyone know of a better way to check? I have a used arm coming and I want to be able to check the bearings quickly. Sorry for the long post!
Thanks,
Don
 
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You can balance the arm so it's floating as you have done, and then see how much force is required to make it move in the vertical direction. For instance, standard weight notebook paper is about .065 grams/square inch (65 milligrams), so just cut out a few squares and see how many you have to put on the end of the tonearm to make it move. I think the Technics SL-1200 arm was specified as something like 7 milligrams, a very low value, that's equivalent to a piece of paper only about 1/4" x 1/2".

Horizontal is more of a problem to check with any accuracy, just balance the arm so it's floating freely, with anti-skate set to zero, and very slightly nudge the arm, observing it swing smoothly toward spindle with no binding over the complete travel path.
 
The Slider said:
You can balance the arm so it's floating as you have done, and then see how much force is required to make it move in the vertical direction. For instance, standard weight notebook paper is about .065 grams/square inch (65 milligrams), so just cut out a few squares and see how many you have to put on the end of the tonearm to make it move. I think the Technics SL-1200 arm was specified as something like 7 milligrams, a very low value, that's equivalent to a piece of paper only about 1/4" x 1/2".

Horizontal is more of a problem to check with any accuracy, just balance the arm so it's floating freely, with anti-skate set to zero, and very slightly nudge the arm, observing it swing smoothly toward spindle with no binding over the complete travel path.
Click to expand...
I can get it to deflect at about 30 mg. I'm not sure about how much deflection to expect. It moves downward, but not totally to the rest.
 
Arms are always influenced by the cable. Few also have the pivots located exactly at the center of gravity, so there's usually a returning force, or an over-center instability, the latter being very rare. Only arms with high friction will sit motionless at any point of the horizontal or vertical travel.
 
Grbluen said:
Happy Easter everyone!

I'm looking for some help with testing the bearings in my tonearms. I have a relatively new Jelco TK-850M. I think the specs are 30mg in both directions. I have floated the arm, and I'm getting significantly less in both directions. I know lower is better. Does anyone know of a better way to check? I have a used arm coming and I want to be able to check the bearings quickly. Sorry for the long post!
Thanks,
Don
Click to expand...
first is the TT well leveled? if is not you can have a difference reading in each direction.
For gimbal tonearm the pivot should be perfectly to 90 degrees to the surface where was installed.
So I will start checking this first.
then, are you issue about spiking tracks or chartering? (too tight, too lose)
AG.
 
Andre Garcia said:
first is the TT well leveled? if is not you can have a difference reading in each direction.
For gimbal tonearm the pivot should be perfectly to 90 degrees to the surface where was installed.
So I will start checking this first.
then, are you issue about spiking tracks or chartering? (too tight, too lose)
AG.
Click to expand...
Table is perfectly level. I'm asking about testing on used tonearms. I have a used tonearm on the way and I want to be able to check it out thoroughly.
 
Grbluen said:
Table is perfectly level. I'm asking about testing on used tonearms. I have a used tonearm on the way and I want to be able to check it out thoroughly.
Click to expand...
first gentle check for backlash, should be zero, or at least not noticeable.
Install it and play a record, put your finger on top of the pivot, you shouldn't feel and "tingling".If it does, probably one of he bearing is not in good shape.
I am not familiar with Jelco, but is not a knife edge bearing?
AG.
 
Grbluen said:
The used tonearm that I have coming isn't a Jelco. It's a Micro-Seiki.
Click to expand...
I've tested one of my Micro Seiki MA-505 arms and it was better than the 25mg spec using the paper method I mentioned above, at least in the vertical plane, I think it was around 10mg. I just go by the amount of weight that causes the tonearm to move, which I think is the test method used for the spec.
 
Nice, Micro Seiki built some very high quality tonearms. I have a MA-202L (long version, 10") that is a work of art. What model do you have coming?

BillWojo
 
The Slider said:
You can balance the arm so it's floating as you have done, and then see how much force is required to make it move in the vertical direction. For instance, standard weight notebook paper is about .065 grams/square inch (65 milligrams), so just cut out a few squares and see how many you have to put on the end of the tonearm to make it move. I think the Technics SL-1200 arm was specified as something like 7 milligrams, a very low value, that's equivalent to a piece of paper only about 1/4" x 1/2".

Horizontal is more of a problem to check with any accuracy, just balance the arm so it's floating freely, with anti-skate set to zero, and very slightly nudge the arm, observing it swing smoothly toward spindle with no binding over the complete travel path.
Click to expand...
And doing that test on a sl1200mk2, a G and a 12 inch Jelco, both the Technics arms moved a lot with that tiny piece of paper on the headshell, but the Jelco did not move.
Testament to how good a Technics arm really is.
Chris
 
I recently picked up a Audio Technica ATP-12T 10" tonearm off of BarterTown and just tried this test. With a 1/4" X 1/2" piece of notebook paper placed on the headshell it started to deflect downwards and if I blow very lightly on the side it moves in the horizontal plain.
It shows just how good some of these old broadcast arms really are.

Billwojo
 
cafe latte said:
And doing that test on a sl1200mk2, a G and a 12 inch Jelco, both the Technics arms moved a lot with that tiny piece of paper on the headshell, but the Jelco did not move.
Testament to how good a Technics arm really is.
Chris
Click to expand...

Or that the Jelco needs to be adjusted.
 
ConradH said:
Totally uncalibrated and arbitrary, but I blow on the balanced arm gently and expect it to move.
Click to expand...
A really good arm in zero poise balance will respond to a light breath pressure with no bearing play. The Sony PUA-7 with anti-skate off is that good, for example. The ITO arm on my H-K T60 isn't.
 
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